There are motorcycles equipped with, for example, an in-line multi-cylinder engine in which an exhaust system is coupled to the engine and is configured to purify an exhaust gas resulting from combustion and to discharge the resulting exhaust gas outside the motorcycle. Japanese Laid-Open Patent Application Publication No. Hei. 10-103046 discloses such a motorcycle. To be specific, an engine of the motorcycle includes a crankcase, a cylinder block located on the crankcase, and a cylinder head that is located on the cylinder block and has a plurality of exhaust ports that open forward of a vehicle body. An exhaust pipe extends downward from the exhaust ports, under the crankcase, and toward a rear region of the engine.
Then, the exhaust pipe extends upward and further rearward with the exhaust pipe supported on a seat rail of the vehicle body. In another construction, an exhaust pipe extends to a rear region of the engine and further extends rearward to a position horizontally lateral of a rear wheel with the exhaust pipe supported on a lower frame of the vehicle body. The length of the exhaust pipe extending from the exhaust ports of the engine to the rear region of the vehicle body is suitably set depending on engine performance, for example, an engine displacement or an engine speed.
In some exhaust systems, an exhaust gas purifier is disposed at a location of an exhaust pipe under the engine. Typically, the exhaust gas purifier contains a catalyst to purify the exhaust gas flowing therethrough. The catalyst is able to produce a higher purifying effect for an exhaust gas with a higher temperature. A muffler is coupled to a rear portion of the exhaust pipe to reduce a noise of the exhaust gas.
Among components equipped in a motorcycle, an engine is often the heaviest. Therefore, a center of gravity of the motorcycle typically is located in the vicinity of a center of gravity of the engine. In some motorcycles, a center of gravity of the engine and other components is suitably positioned in the vicinity of the center of gravity of the motorcycle. In the motorcycle equipped with the exhaust system constructed as described above, the elongated exhaust pipe extends in a longitudinal direction of a vehicle body of the motorcycle. Further, a muffler, which is a component with a heavy weight, is disposed distant rearward from the center of gravity of the motorcycle. As a result, it is difficult to position the components in the exhaust system in the vicinity of the center of gravity of the motorcycle.